Outline of Overall Rationale for Virtual Beanstalk Project

I.                   Long-term permanent station keeping at stratospheric altitudes can be useful for many applications.

A.    The high altitude provides a broad area for broadcast and visual observation.

B.    The high altitude provides considerable potential energy of position.

C.    Stratospheric conditions provide low air pressure, consistent winds, and excellent visibility.

D.    Stratospheric conditions offer insulation from the effects of weather in the troposphere.

II.                Tethered aerostats can remain fixed on station indefinitely (months or longer) without fuel or intervention.

A.    Tethered aerostats needn’t vent gas to stabilize their altitude, so they can carry extra lift gas to offset losses.

B.    The tether itself has a small enough cross-section that wind on the rope alone does not adversely affect performance.

C.    Tethered aerostats will not drift outside of a radius determined by tension in their tether, and they require no guidance of any kind.

D.    Tethered aerostats can be built to carry large payloads.

III.              It should be possible to build a tethered aerostat that can ascend through the entire troposphere and into the stratosphere.

A.    Existing tethered aerostats, such as kite blimps and other designs, have been limited to less than three kilometers altitude (well below the stratosphere).  This is primarily due to limitations of their designs, which cannot deal with the midlevel winds when only partially inflated and are often too heavy.

B.    Existing new materials, such as high density polyethylene, are strong, sufficiently lightweight and very durable under the required operating conditions.

C.    New methods should allow a tethered aerostat to undergo the required fifteen-fold expansion of its lift gas required to ascend to the stratosphere and still retain adequate structural strength and aerodynamic trim to deal with midlevel winds.

IV.             A regular maintenance routine, enabled by use of an elevator capable of traversing the entire tether, can dramatically extend both the mission duration and range of mission profiles.

A.    The elevator can be propelled by one of several different means, as it need only traverse less than 20 miles along a very strong rope.

B.    An elevator or unmanned instrument pack on the tether can perform midlevel missions at any altitude along the tether.

C.    The elevator can transfer maintenance crews and supplies.

D.    With the advent of lightweight versatile pressure suits and the existing pool of experience with maintenance under vacuum conditions acquired by national space programs, it should be possible to devise a suitable maintenance routine for a stratospheric platform.